When a vehicle travels reversely on an express way, a traffic accident such as accidental contact may occur. For example, when the vehicle goes out to a main road of the express way by mistake from an entrance ramp of a parking place (i.e., PP) such as a parking area and a service area on the express way, the vehicle travels reversely on the express way, so that possibility of traffic accident attributed to the reverse run becomes high. Thus, it is required to alert a driver to the reverse run after the reverse run is detected.
In electric map data used for an in-vehicle navigation device, the main road of the express way and a passage of the parking place such as the entrance ramp and an exit ramp are distinguished in link data. Information about a traveling direction is attached to the link data of the main road and the passage. Here, the information of the traveling direction is defined as a one-way traffic attribute data. Accordingly, when it is determined whether an actual traveling direction of the vehicle follows the one-way traffic attribute data, the reverse run on the passage of the parking place is determined. Then, it is possible to alert the reverse run.
However, in the parking place, there are three types of roads. When the vehicle travels on a certain type of the roads, the alert of the reverse run may not be required. The three types of the roads in the parking place on the express way will be explained with reference to FIG. 1. FIG. 1 shows the three types of the roads in the parking place. A solid line in FIG. 1 represents the main road of the express way. A broken line in FIG. 1 represents the passage in the parking place. A part IA of the passage surrounded with a dotted ellipsoid represents the entrance ramp of the parking place. A part IB of the passage surrounded with a dotted ellipsoid represents a parking area road of the parking place. A part IC of the passage surrounded with a dotted ellipsoid represents the exit ramp of the parking place. In FIG. 1, an arrow represents the one-way traffic attribute data.
As shown in FIG. 1, there are three types of the roads, i.e., the entrance ramp, the parking area road and the exit ramp in the parking place. When the vehicle travels on the parking area road, the vehicle sometimes travels reversely in order to park the vehicle in a parking frame. In this case, the vehicle travels reversely by necessary so that the traveling direction of the vehicle does not follow the one-way traffic attribute data. The driver does not intend to go out to the main road of the express way in a reverse manner. If the reverse run of the vehicle in the parking place is detected, and the reverse run is alerted, the alert may bother the driver. Thus, it is preferable to specify the entrance ramp and the exit ramp, and when the vehicle travels on the entrance ramp and the exit ramp in a reverse manner, the reverse run is alerted.
In view of the above difficulty, for example, JP-A-2003-151077 teaches that the reverse run is detected with using an in-road wireless element only when the vehicle travels on the entrance ramp and the exit ramp in the parking place. The on-road wireless element is arranged along with the entrance ramp, i.e., approach way from the main road of the express way to the parking place and the exit ramp, i.e., exit way from the parking place to the main road of the express way. Specifically, in JP-A-2003-151077, the on-road wireless element transmits information about the number of beacon, which specifies the entrance ramp and the exit ramp, to an in-vehicle wireless element. When the in-vehicle wireless element receives the information of the number of the beacon, the in-vehicle wireless element stores the information of the number of the beacon. When the in-vehicle wireless element receives the information of the same number of the beacon again, it is determined that the vehicle reversely travels on the entrance ramp or the exit ramp. Then, the alert of the reverse run is output.
JP-A-2007-139531 teaches that a conventional in-vehicle navigation device includes a database for providing reverse run prohibition road information of an automobile limited road (i.e., express way). Specifically, the road corresponding to the entrance ramp and the exit ramp is defined as a reverse run prohibition road, which is preliminary stored as the map data. Based on the position of the vehicle, the actual traveling direction of the vehicle and the reverse run prohibition road information, it is determined whether the vehicle travels on the reverse run prohibition road in a reverse direction. When it is determined that the vehicle travels reversely, the alert of the reverse run is output.
However, in JP-A-2003-151077, it is necessary to arrange the on-road wireless element on each entrance ramp and each exit ramp of a respective parking place of the express way, so that an infrastructure should be built up. Thus, a cost of the infrastructure is very high, and a system for the infrastructure is a large-scale system. Thus, it is difficult to realize the system.
In JP-A-2007-139531, it is necessary to attach the link data to the map data, and the link data provides to distinguish the entrance ramp, the parking area road and the exit ramp in the parking place. However, a conventional map data usually includes the link data, which provides to distinguish merely the main road of the express way and the road in the parking place. Thus, it is necessary to provide new map data. When the new map data is formed, time and effort are required. Thus, it is difficult to realize the new map data.